3
3-1 System Description - Strider Transmitter Link
Strider Link Series
SRFStrider-161004A-REV.A
Sinteck Sistemas Eletrônicos Ltda.
3.1 Strider Transmitter Link - Multiplexx - Audio processor and stereo generator
cards
The Strider Transmitter Link is a high fidelity broadband FM transmitter with a power output
of 8 Watts. It is capable of transmitting the program signal and two multiplex subcarriers with
little degradation of signal quality over one link. The linearity and FM noise characteristics of
the direct FM oscillator are exceptional. The transmitter is modular in construction and
operation, and the system description given below follows the signal flow through the varios
modules and its cards.
The system assembly drawings are located in Section “ Schematics” along with the
module schematics and system schematics are at the end of this manual.
Fm Synthesizer
The baseband signal from the audio inputs modulates the frequency modulated oscillator
(FMOSC) in the VCO Block. The FMOSC consists of a 170-450MHz ultralinear, very low
noise VCO which is phase locked to a crystal-controlled reference oscillator. The phase lock
loop contains the frequency programming mode which allow the synthesizer to be changed
in frequency steps of 250kHz (standard) 25kHz or 100kHz in some models. The RF signal
will d-75kHz (composite) or +-50kHz (mono) from the carrier. The output power of
the VCO is approximatelly 5 milliwatt.
RF 50mW amplifier
In to the VCO block, there is a smaller RF amplifier section, that amplifiers 5mW from the
VCO output to 50mW through of 2 transistors.
RF 8W amplifier
The RF amplifier module internally consists of a two-stage MOSFET design, which
amplifies the input signal (50mW typ.) To the nominal 8W transmitter output. The output is
filtered to attenuate all higher order harmonics to a level of at least -60dBc. The output is
sampled via a dual directional coupler with detectors that provide an indication of the
forward and reflected power of the RF amplifier.The final stage current and voltage is
sampled and metered in this module.
Transmitter Control
The Transmitter Control section of the audio and power supply board has several functions.
One of these is to sense the PLL LOCK detect signal from the RF module. If this module
goes out of lock, then the radiate control logic circuit provides a signal to the power supply to
turn off the +7,2 VDC supply to the RF power module, causing the transmitter to stop
radiating. Also, this section detects if the VSWR level is more than permised, so the
transmitter control turn off the DC level to the RF power module. All of these parameters can
be view through the LCD on the front panel.
Metering and Status
The Metering and Status circuitry on the audio, Power Supply and RF sections conditions
the various system parameter samples for accurate meter indications, and drives the status
LEDs on the front panel.
03/P/20
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